I was also going to say The Shining. Despite having what may be the most blood on screen at once in movie history (I've heard Braindead might hold that record), and a couple of rapid gory frames scattered around, it really isn't that gory. And it's one of the best horror movies.

Yeah, but it's become part of pop culture, there's parodies in dozens of different things. It'd be hard to find somebody who isn't already familiar with that scene going in to Alien, although I guess it is decidedly more graphic and intense than a spoof of it.